The present invention relates to a method of vaporizing additives in metal melts.
Additives are vaporized under atmospheric pressure in a metal melt by means of known equipment which includes a vessel having a chamber into which the additives can be introduced from the outside and in which the additives are vaporized under the influence of the metal melt which flows from the vessel into the chamber through appropriately arranged openings.
The prerequisite for this vaporization is the characteristic of the additives, such as, lithium, calcium, magnesium, etc. to develop at the temperature of the metal melt a vapor pressure which exceeds the metallostatic pressure of the metal melt prevailing within the chamber.
The vaporized additives escape from the chamber into the metal melt through some of the openings mentioned above. If the geometric configuration of the openings, the total cross-sectional area of the openings and the chamber volume do not have the proper relationship to the level of the bath of metal melt, or the volume of the vessel, or the content of certain elements obtained in the metal melt, such as, sulphur, hydrogen or oxygen, it is not possible to obtain an optimum vaporization with a high degree of efficiency and a reproducible residual content of the additives or the elements in the metal melt. All of these influences result in a certain time required for the vaporization of the additives.
Very long or very short vaporization time cause a decrease of the efficiency of the additives and of the accuracy in obtaining a predetermined residual content of the additives or of the elements in the metal melt. When the vaporization time is too long or the size of the openings in the chamber is too small, these openings may be clogged due to solidification of the metal melt or of the reaction products. A vaporization time which is too short results in a vehement reaction with substantial slopping of metal melt. In both these cases, additional technical problems occur with respect to safety of operation.
It is, therefore, the primary object of the invention to obtain an accurate reproducibility of the parameters of the end product, for example, the residual magnesium content, the degree of the deoxidation, etc. and to improve the efficiency of the additives.